Heat exchanger and method of manufacture therefor

ABSTRACT

A heat exchange apparatus comprising a tube and plate and a method of manufacture for the heat exchange apparatus. The method includes the steps of forming the tube, such as by extrusion, to provide an external attachment appendage which, in the illustrative embodiment, is T-shaped in cross section, forming spaced parallel slots in a thin plate, offsetting the material of the plate along and adjacent the slots to accommodate the Tshaped attachment appendage in sliding relationship therewith and, finally, compressing the tube against the plate to lock the two elements together and to provide a flush surface on the side of the plate which is opposite the tube. The offsetting need not be carried out as a separate step but may take place simultaneously with the final compression. In a specific embodiment, the mechanical bond is enhanced by forming spaced parallel flanges on the interior surface of the attachment appendage.

llntte States Patent [191 [111 3 858 647 a 9 Hickman et al. 1 Jan. 7,1975 [54] HEAT EXCHANGER AND METHOD OF 3,138,658 6/1964 Weimer 29/521 uxMANUFACTURE THEREFOR Primary Examiner-Richard J. Herbst 76 l t St 1 menOrs f ZfIf 'I L E'J Q E L E 4886 Assistant Exammer-D. C. Reiley, III

S. Adrian Hwy B of Adrian Attorney, Agent, or Firm-Thomas N. Young Mich.49221 [57] ABSTRACT 22 F] d: A 10 973 1 16 ug ,1 A heat exchangeapparatus comprising a tube and [21] Appl. No.: 387,524 plate and amethod of manufacture for the heat cx- Related U S Application Datachange apparatus. The method includes the steps of Comi ti fs N 344 245M h 23 forming the tube, such as by extrusion, to provide an 1973 g g ggarc external attachment appendage which, in the illustrative embodiment,is T-shaped in cross section, forming [52] U S Cl 165/171 29/157 3 C62/515 spaced parallel slots in a thin plate, offsetting the ma- H3/l'l8165/49 terial of the plate along and adjacent the slots to ac- [51] IntCl Fzsf 1/32 821d 53/02 p 15/26 commodate the T-shaped attachmentappendage in [58] Fie'ld 29/l573 0 62/515 sliding relationship therewithand, finally, compressing 1 29/515 the tube against the plate to lockthe two elements together and to provide a flush surface on the side ofthe plate which is opposite the tube. The offsetting need [56]References Clted not be carried out as a separate step but may takeUNITED STATES PATENTS place simultaneously with the final compression.in a 2,171,790 9/1939 specific embodiment, the mechanical bond is en-2,5161586 7/1950 hanced by forming spaced parallel flanges on theinterior surface of the attachment appendage. 2:867:417 1/1959 8 Claims,6 Drawing Figures PATENIEB JAN 71975 SHEET 10F 2 PATENTEB JAN 7 I975SHEET 2 BF 2 HEAT EXCHANGER AND METHOD OF MANUFACTURE THEREFOR This is aContinuation-In-Part application of US. Ser. No. 344,245, filed Mar. 23,1973, now US. Pat. No. 3,827,485, entitled Heat Exchanger And Method ofManufacture Therefor.

This invention relates to heat exchanger apparatus and to a method ofmanufacture for heat exchanger apparatus which involves the assembly ofa tube and plate for thermal transfer therebetween.

BACKGROUND OF THE INVENTION Heat exchanger apparatus for use ascondensers, evaporators, radiatiors, and the like typically comprise thecombination of a fluid conduit of serpentine configuration and one ormore fins or plates which enlarge the effective surface area of theconduit for efficient thermal exchange. The manufacture of such heatexchange apparatus typically comprises the steps of forming a tube orother conduit means and joining it to the plate by an operation such asbrazing, epoxy bonding, or roll-bonding.

The brazing, epoxy bonding, and/or roll-bonding processes are relativelyexpensive in themselves as compared to mechanical bonding techniquesand, moreover, typically require the use of capital equipment which addsstill further expense to this process. Therefore, although the productswhich result from the brazing, epoxy bonding, and/or roll-bondingoperations are satisfactory, there exists a need for a simple andeconomical method of heat exchanger fabrication which involves a purelymechanical bonding process.

BRIEF SUMMARY OF THE INVENTION This invention provdes a simple andeconomical method of fabricating heat exchanger apparatus through themechanical bonding of a tube and a plate for efficient thermal transfertherebetwen. Briefly stated, the method involves the fabrication of atube having an external attachment appendage and the formation of one ormore slots in a plate so as to receive the attachment appendage. Eitherbefore or after the slot and attachment appendage are interconnected,the material of the plate is offset along and adjacent the slot by atleast the thickness of the attachment appendage such that when theappendage is disposed in the slot and in the offset portion, asubstantially flush surface is provided on the side of the plate whichis opposite the tube. In the preferred embodiment of the presentinvention, the final bond is achieved by compressing the tube againstthe plate thereby to partially flatten the tube into good thermaltransfer configuration while at the same time tightening the mechanicalbond and smoothing the flush side of the plate.

In the ilustrative embodiment of the invention hereinafter described indetail, the tube is preferably of extruded aluminum and has an integral,T-shaped (in cross section) attachment appendage. The manufacturingoperation as illustratively described involves the formation of aplurality of spaced, parallel slots in the plate and the prior bendingof the tubes so as to form straight portions which register with theslots in the plate. The attachment appendage is trimmed from the tubealong the curved portions between the straight portions whereupon thetube may be simply inserted by sliding the attachment appendages intothe offsets and slots. As stated above, this joining operation isfollowed by a compression step which results in an inexpensivelyfabricated yet highly durable and efficient heat exchange device.

The mechanical bond may be enhanced if desired by forming sharp,parallel flanges on the surface of the attachment appendage nearest thetube; i.e., the interior surface of the appendage. This enhances theintegrity of the mechanical bond by preventing lateral separation of theplate portions on opposite sides of a slot during any later formingoperations which might take place.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is an isometric view with partsbroken away of an illustrative tube and plate apparatus for carrying outthe invention;

FIG. 2 is an end view of a portion of the tube and plate illustrated inFIG. 1 and showing the result of the compression step;

FIG. 3 is a plan view ofa representative portion of a finalized productmanufactured inaccordance with the invention;

FIG. 4 is a side view or sectional view along the section line 4-4 ofFIG. 3;

FIG. 5 is a perpsective drawing of an oval heat exchanger unit embodyingthe invention; and,

FIG. 6 is a partial view of the unit of FIG. 5 taken along a sectionline 6-6.

DETAILED DESCRIPTION OF THE SEPCIFIC EMBODIMENT Referring now to thedrawings and particularly to FIG. 1, there is shown an apparatus for theassembly of a heat exchange device which, in accordance with the presentinvention, comprises an extruded aluminum tube 10 suitable for theconveyance of various fluids and having an external attachment appendage12 which is integral with the tube and T-shaped in cross section. FIG. 1also illustrates a plate 14 of aluminum or other suitable thermallyconductive material, the plate 14 being subjected to a number ofindustrial processing steps so as to receive the tube 10 into acooperative relationship therewith as hereinafter described. In thatcooperative relationship an efficient thermal transfer relationshipbetween the tube ]l0 and the plate 14 exists.

As shown in FIG. 1, tube 10 is formed with the integral T-shapedattachment appendage l2 and is then bent to define a curved portion 16separating two parallel straight portion A and B. The externalattachment appendage 12 is then trimmed from the tube 10 along theentire length of the curved portion 16, but is left intact along thestraight portions A and B.

The tube 10 shown in FIGS. l and 2 is extruded aluminum having an outerdiameter of 0.312 inch and a wall thickness of approximately 0.035 inchand a spacing between the straight portions A and B of from 1 inch toseveral inches. These dimensions are, of course, given by way ofillustration only as they bear no critical relationship to the inventionwhatsoever. The curved portion 16 may be formed in accordance with theconfiguration shown in the drawings or. alternatively, may be formed asa continuous radius.

Looking now to the plate l4,this member is also preferably formed ofaluminum in a suitable thickness so as to be susceptible of the formingoperations described herein. Slots 18 and 20 are formed within theinterior boundaries of the plate in parallel relationship and spacedapart so as to register with and be of equivalent length to the lengthsof the attachment appendage 12 along the straight portions A and B oftube 10. The material of the plate 14 along and adjacent the slots 18and 20 is then offset, as shown in FIG. 1, by an amount at least equalto and preferably twice the thickness of the top of the T-shapedappendage 12. The greater offset distance is generally required wherethe slots 18 and 20 do not open to a border or edge of the plate 14whereas a lesser offset distance is satisfactory where the slots do opento an edge of the plate for obvious reasons. It will be noted that thedevice of FIG. 3 illustrates the case where the slots have terminal endsspaced from the boundaries of the plate 14.

Tube and plate 14 are then interconnected by lining up the attachmentappendage lengths with the slots and sliding the appendage lengths intothe slots so as to fill the slots and offset areas of the plate 14. Atthis state in the assembly process, the tube 10 is relatively loselyconnected to the plate 14 but is essentially in the final position.

Looking to FIG. 2, the assembly of the tube 10 and plate 14 is thensubjected to a compression step wherein opposite platens 22 and 24 of anhydraulic press or the like are brought to bear against the top of theplate 14 and the bottom of the tube 10 soas to compress the tube againstthe plate within the boundaries of spacer blocks 26 thereby locking theassembly together and bringing all abutting surfaces into close contactto improve the thermal conductivity. In addition, the offset area iscompressed along with the T- shaped appendage 12 so as to form asubstantially flush surface on the side of the plate 14 which isopposite the tube 10. Obviously, a compression roller arrangement may besubstituted for the platens 22 and 24 shown in FIG. 2. Also a die may besubstituted for the platen 24 and blocks 26 in a production machine.

As best shown in FIGS. 3 and 4, the tube 10 is typically formed in aserpentine configuration so as to be characterized by a plurality ofparallel, spaced, straight portions joined by a plurality of curvedportions, the T-shaped atachment appendage 12 being trimmed from thetube 10 throughout the length of the curved portions, but left intactthroughout the parallel spaced straight portions. The terminal ends ofthe tube 10 may, of course, occur at variouss points along the lengththereof in accordance with the specific application of the heat exchangedevice manufactured hereunder.

It will be understood that the attachment appendage may be of variousconfigurations including not only the T-shaped configuration shown inthe drawings but also for example, an L-shape. The appendage is notnecessarily extruded in its final form, but may be bent or folded duringthe compression step according to the specific shape thereof. The flushsurface evident in FIGS. 2 through 4 may be accomplished by forming theoffset after assembly of the tube 10 and plate 14 rather than beforeassembly as described above. In accordance with this alternative, theslots 18 and may be cut into the plate 14 so as to extend fully to theedge of the sheet. The appendage 12 is then disposed in the slot and thecombination is compressed in a platen and die combination similar tothat of FIG. 2 wherein the upper platen 22 is flat and the lower platenor die main tains the assembly shape by confinement. The compressionstep displaces the appendage 12 downwardly so as to cold-form the offsetduring the compression and shaping of the assembly. The result is aflush upper surface of the assembly and a secure bond between tube andplate.

It is to be understood that the flush surface of the combined plate 14and tube 10 is desirable inasmuch as the heat exchange device is oftenleft exposed on the flush side in the final assembly, such as in arefrigerator, cooler, freezer, or the like. However, the majoradvantages of the invention arise from the economical and effectivesecurement of parts together and these advantages obtain even where theresulting surface is not perfectly flat. Accordingly, the full offset ofthe appendage area of the plate is not essential to the invention. Theheat exchange apparatus is typically coated by spraying or dipping witha suitable preservative material, such as an acrylic plastic, to meetUnderwriters Laboratory and other requirements. Such dipping or spraycoating tends to fill the small cracks or voids which exist between thetop of the T-shaped appendage l2 and the adjacent plate areas, as bestshown in FIG. 2, thus, to make the final assembly easy to clean as wellas attractive in appearance.

FIG. 5 illustrates an oval or rectangular heat exhcanger unit 28 such asone might find used in a refrigerator or freezer. The unit 28 comprisesa large flat plate 14a slotted as described above the receive a tube 10awhich is bent into a serpentine configuration and which includes anattachment appendage 12a. The tube 10a and plate 14a are joined in thefashion described above with reference to FIG. 2 and, thereafter, thecombined unit is bent into the closed oval or rectangular form shown. Anoverlapped and bonded seam 30 holds the unit in the proper shape.

It can be seen in FIG. 5 that the flat surface of the attachmentappendage 12a is flush with the interior surface of the plate 14a toprovide a smoooth and attractive unit for the receipt of goods to berefrigerated.

To counteract any tendency for the slots to widen and separate laterallyfrom the tube 10a when the plate 14a is bent into the oval shape, theappendage 12a may be formed as shown in FIG. 6 to include the spacedparallel flanges or ribs 32. The flanges 32 are formed during extrusionof the tube 10a and exhibit a relatively sharp point facing the tube.Accordingly, the final compression step previously described tends todeform the plate 14a around the points of the flanges 30 to firmlyanchor the plate portions against lateral movement relative to the tube10a.

The invention has, of course, been described by reference to anillustrative embodiment and, accordingly, the foregoing specification isnot to be construed in a limiting sense.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A heat exchanger apparatus comprising: a tube having a substantiallyT-shaped integral attachment appendage, the interior surface of the topof said appendage having substantially pointed flanges formed therein, aplate having a through slot formed therein, and an offset along andadjacent said slot, said attachment appendage being disposed in saidslot and offset and of such configuration as to provide a substantiallyflush surface on the side of the plate opposite the tube, the tube beingcompressed against the plate, said plate being mechanically deformedaround said flanges to enhance the strength of the mechanical bondbetween the tube and the plate transversely of the tube, the combinedunit being bent into a closed compartmental form with the seam bonded tohold the unit in shape.

2. A method for assembling a tube having an external attachmentappendage and a plate for thermal transfer between the tube and platecomprising the steps of extruding a metal tube having an integralattachment appendage along one side thereof with at least onesubstantially pointed flange formed in a surface thereof opposite thetube, forming at least one slot in and through the plate, sliding theappendage into the slot, and compressing the tube against the plate tomechanibond the plate and the tube, whereby the step of compressingtends to deform the plate locally around the flange to enhance themechanical bond transversely of the tube.

3. A method for assembling a tube having an external attachmentappendage and a plate for thermal transfer between the tube and platecomprising the steps of extruding a metal tube having an integralattachment appendage along one side thereof with at least onesubstantially pointed flange formed in a surface thereof opposite thetube, forming at least one slot in and through the plate sliding theappendage into the slot, and compressing the tube against the plate tomechanically bond the plate and the tube and to form an offset in saidplate along and adjacent said slot which receives said appendage so thata substantially flush surface is provided on the side of the plateopposite the tube, whereby the step of compressing tends to deform theplate locally around the flange to enhance the mechanical bondtransversely of the tube.

4. The method defined in claim 3 including the further step of bendingthe tube to form a curved tube portion and a straight tube portion andtrimming the attachment appendage from the tube along the curvedportion, the straight portion corresponding in length to the length ofthe slot.

5. The method defined in claim 3 wherein the compression step results inan offset in said plate along and adjacent said slot.

6. The method defined in claim 3 wherein the slot has a pair of terminalends which are spaced from and within the boundaries of the plate.

7. A method for assembling a tube having an external attachmentappendage and a plate for thermal transfer between the tube and platecomprising the steps of: extruding a metallic tube having a T-shapedattachment appendage with at least one substantially pointed flangeformed in a surface thereof opposite the tube, bending the tube having aT-shaped attachment appendage, bending the tube into a serpentineconfiguration having a plurality of curved portions and a plurality ofparallel straight portions, trimming the external attachment appendagefrom the curved portions, forming a plurality of parallel slots in andthrough a metallic plate of such length and spacing as to correspond tothe length and spacing of the straight portions of the tube, offsettingthe plate along and adjacent to the slots by at least the thickness ofthe T-shaped attachment appendage, sliding the atachment appendagesegments into the spaced slots and offset portions and compressing thetube against the plate with the plate between the tube and appendage topto provide a mechanical connection between the tube and plate and tofurther provide a substantially flush surface on the side of the plateopposite the tube whereby the step of compressing tends to deform theplate locally around the flange to enhance the mechanical bondtransversely of the tube.

8. A method for assembling a tube and a plate for thermal transfertherebetween wherein the tube has formed therewith an externalattachment appendage having at least one substantially pointed flangeformed in a surface thereof opposite the tube, the method comprising thesteps of: forming at least one slot in and through the plate, forming anoffset in the plate along and adjacent to the slot, joining theappendage and slot, and compressing the tube against the plate toprovide a mechanical bond between the tube and plate, whereby the stepof compressing tends to deform the plate locally around the flange toenhance the mechanical bond transversely of the tube.

1. A heat exchanger apparatus comprising: a tube having a substantiallyT-shaped integral attachment appendage, the interior surface of the topof said appendage having substantially pointed flanges formed therein, aplate having a through slot formed therein, and an offset along andadjacent said slot, said attachment appendage being disposed in saidslot and offset and of such configuration as to provide a substantiallyflush surface on the side of the plate opposite the tube, the tube beingcompressed against the plate, said plate being mechanically deformedaround said flanges to enhance the strength of the mechanical bondbetween the tube and the plate transversely of the tube, the combinedunit being bent into a closed compartmental form with the seam bonded tohold the unit in shape.
 2. A method for assembling a tube having anexternal attachment appendage and a plate for thermal transfer betweenthe tube and plate comprising the steps of extruding a metal tube havingan integral attachment appendage along one side thereof with at leastone substantially pointed flange formed in a surface thereof oppositethe tube, forming at least one slot in and through the plate, slidingthe appendage into the slot, and compressing the tube against the plateto mechanibond the plate and the tube, whereby tHe step of compressingtends to deform the plate locally around the flange to enhance themechanical bond transversely of the tube.
 3. A method for assembling atube having an external attachment appendage and a plate for thermaltransfer between the tube and plate comprising the steps of extruding ametal tube having an integral attachment appendage along one sidethereof with at least one substantially pointed flange formed in asurface thereof opposite the tube, forming at least one slot in andthrough the plate sliding the appendage into the slot, and compressingthe tube against the plate to mechanically bond the plate and the tubeand to form an offset in said plate along and adjacent said slot whichreceives said appendage so that a substantially flush surface isprovided on the side of the plate opposite the tube, whereby the step ofcompressing tends to deform the plate locally around the flange toenhance the mechanical bond transversely of the tube.
 4. The methoddefined in claim 3 including the further step of bending the tube toform a curved tube portion and a straight tube portion and trimming theattachment appendage from the tube along the curved portion, thestraight portion corresponding in length to the length of the slot. 5.The method defined in claim 3 wherein the compression step results in anoffset in said plate along and adjacent said slot.
 6. The method definedin claim 3 wherein the slot has a pair of terminal ends which are spacedfrom and within the boundaries of the plate.
 7. A method for assemblinga tube having an external attachment appendage and a plate for thermaltransfer between the tube and plate comprising the steps of: extruding ametallic tube having a T-shaped attachment appendage with at least onesubstantially pointed flange formed in a surface thereof opposite thetube, bending the tube having a T-shaped attachment appendage, bendingthe tube into a serpentine configuration having a plurality of curvedportions and a plurality of parallel straight portions, trimming theexternal attachment appendage from the curved portions, forming aplurality of parallel slots in and through a metallic plate of suchlength and spacing as to correspond to the length and spacing of thestraight portions of the tube, offsetting the plate along and adjacentto the slots by at least the thickness of the T-shaped attachmentappendage, sliding the atachment appendage segments into the spacedslots and offset portions and compressing the tube against the platewith the plate between the tube and appendage top to provide amechanical connection between the tube and plate and to further providea substantially flush surface on the side of the plate opposite the tubewhereby the step of compressing tends to deform the plate locally aroundthe flange to enhance the mechanical bond transversely of the tube.
 8. Amethod for assembling a tube and a plate for thermal transfertherebetween wherein the tube has formed therewith an externalattachment appendage having at least one substantially pointed flangeformed in a surface thereof opposite the tube, the method comprising thesteps of: forming at least one slot in and through the plate, forming anoffset in the plate along and adjacent to the slot, joining theappendage and slot, and compressing the tube against the plate toprovide a mechanical bond between the tube and plate, whereby the stepof compressing tends to deform the plate locally around the flange toenhance the mechanical bond transversely of the tube.